摘要:

AbstractPotentially fatal sodium imbalance occurs in captive and free‐ranging pinnipeds and is associated with a variety of stressors. We sought to determine the role of adrenal hormones, principally aldosterone, in the development of this condition. To induce hyponatremia, two ringed seals,Phoca hispida, were maintained in fresh water and fed a low‐sodium diet; as controls, two other ringed seals were held in salt water and received a salt‐supplemented diet. After 3–6 mo, adrenocorticotropic hormone (ACTH) was used to assess adrenocortical function. In normonatremic control seals, ACTH produced a 2‐j‐fold increase in circulating cortisol and a 7‐fold increase in aldosterone. One of the experimental seals maintained normal plasma sodium levels, and ACTH elicited an exaggerated aldosterone response. The other salt‐deprived seal became hypo‐natremic, and ACTH had little effect on plasma aldosterone levels. An ACTH stimulation test performed on a spontaneously hyponatremic harp seal, P.groenlandica, which had been maintained in a salt‐rich environment, failed to elicit cortisol or aldosterone secretion from the adrenal cortex. This study demonstrated the unusual sensitivity of the seal's zona glomerulosa to central stimulation, providing a mechanism through which the stress response might exhaust adrenal hormone reserves or desensitize the cortex to other ph

ISSN:0824-0469    

DOI:10.1111/j.1748-7692.1986.tb00133.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractA review of our whale observations of more than 25 years indicated that each of the species commonly observed within 35 km of Cape Cod reacted differently to stimuli from human activities, and that these responses have gradually changed with time. Over the years of exposure to ships, for example, minke whales (Balaenoptera acutorostrata) have changed from frequent positive interest to generally uninterested reactions, finback whales (B. physalus) have changed from mostly negative to uninterested reactions, right whales (Eubalaena glacialis) have apparently continued the same variety of responses with little change, and humpbacks (Megaptera novaeangliae) have dramatically changed from mixed responses that were often negative to often strongly positive reactions. These reactions appeared to result mostly from three types of stimuli: primarily underwater sound, then light reflectivity, and tactile sensation. The whale reactions were related to their assessment of the stimuli as attractive, uninteresting or disturbing, their assessment of the movements of the sources of the stimuli relative to their own positions, and their assessment of the occurrence of stimuli as expected or unexpected. Whale reactions were modified by their previous experience and current activity: habituation often occurred rapidly, attention to other stimuli or preoccupation with other activities sometimes overcame their interest or wariness of stimuli, and inactivity seemed to allow whales to notice and react to stimuli that otherwise might have been ignored. The changes over time in the reactions of whales to stimuli from human activities were gradual and constantly varying with increased exposure to these activities.

ISSN:0824-0469    

DOI:10.1111/j.1748-7692.1986.tb00134.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractThe partial skull and mandible of an unidentified halitheriine dugongid, collected from the Early Miocene Nye Mudstone in Lincoln County, Oregon, USA, is the earliest record of the Sirenia in the eastern Pacific Ocean. It is probably earlier than Early or Middle Miocene sirenians recently found in Peru, and is definitely earlier than any known from California or Baja California. However, it appears to be slightly younger than fossil sirenian remains recently reported from Late Oligocene rocks in Japan. The Oregon specimen is also the most northern record of the Sirenia on the west coast of North America prior to the Pleistocene although other sirenians did evidently reach and surpass such latitudes by the Late Miocene when a dispersal took place from America to the North Pacific coasts of the Old World. The Oregon specimen probably represents sirenians that spread to the North Pacific from the Caribbean, quite possibly prior to the Miocene. The Nye Mudstone was deposited during the warmest period of the Neogene on the coast of Oregon, and it does not seem necessary to postulate a greater degree of cold‐tolerance for the Oregon sirenian than is exhibited by living sea cow

ISSN:0824-0469    

DOI:10.1111/j.1748-7692.1986.tb00135.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractThe Pliocene fossil whale,Eschrichtius davidsoniiCope 1872, is actually a balaenopterid mysticete referable to the modern genusBalaenopteraLacépède 1804. Redescription of the holotype of B.davidsonii(a partial left dentary), together with the discovery and description of a nearly complete right dentary referrable to this taxon, demonstrates the taxonomic and systematic affinities ofBalaenoptera davidsonii.Although originally thought to be Miocene in age, newspaper accounts of 1872 indicate that the holotype of B.davidsoniiwas actually collected from fossiliferous sandstones here referred to the San Diego Formation of Late Pliocene age (equivalent to the Blancan North American Land Mammal Age).Comparisons between the dentary of B.davidsoniiand dentaries of other extant and fossil balaenopterids allow recognition of several taxonomically useful mandibular characters (i.e., degree of longitudinal curvature of horizontal ramus and form of transverse cross‐sectional outlines). A taxonomic review of other nominal Neogene species ofBalaenopterafrom Europe and eastern North America is an initial attempt at stabilizing the confusing nomenclatural history and taxonomy of this group. In this regard, the genusBurtinopsisVan Beneden 1872 is placed in synonymy withBalaenoptera.Generic reassignment of the fossil rorqualBalaenoptera davidsonii(Cope 1872) creates a nomenclatural problem of homonymy with the extant minke whaleBalaenoptera davidsoniScammon 1872. As Cope's species is a senior homonym of Scammon's, suppression of Scammon's name is recommended. The new trinomenBalaenoptera acutorostrata scammonin. ssp. is here proposed for the North Pacific minke wh

ISSN:0824-0469    

DOI:10.1111/j.1748-7692.1986.tb00136.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

ISSN:0824-0469    

DOI:10.1111/j.1748-7692.1986.tb00137.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

ISSN:0824-0469    

DOI:10.1111/j.1748-7692.1986.tb00138.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

ISSN:0824-0469    

DOI:10.1111/j.1748-7692.1986.tb00139.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

ISSN:0824-0469    

DOI:10.1111/j.1748-7692.1986.tb00140.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

ISSN:0824-0469    

DOI:10.1111/j.1748-7692.1986.tb00141.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

ISSN:0824-0469    

DOI:10.1111/j.1748-7692.1986.tb00142.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY